Switching noise sometimes arises at the time of switching operation of a power semiconductor, such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). A MOSFET structure proposed in view of inhibiting occurrence of switching noise increases a difference between gate-to-drain capacitance achieved in an activated state and gate-to-drain capacitance achieved in a deactivated state, thereby decreasing a jump voltage of a drain voltage (see; for example, Patent Document 1).
Moreover, a silicon carbide MOSFET requires a withstand voltage which enables the MOSFET to withstand a voltage of the order of 1000V, and for this reason, a structure where a high voltage is applied in a reverse-bias direction to a p-type base layer and an n-type drift layer which have comparatively low concentration levels is employed for the silicon carbide MOSFET, and it is shown that the withstand voltage is determined by a depletion layer formed in a p-n junction (see; for example, Patent Document 2).
Further, there is a description about a semiconductor device using silicon carbide in which a silicon carbide layer is made semi-insulating by implanting protons and He2+ ions into the layer (see; for example, Patent Document 3).    Patent Document 1: JP-A-2004-6598 (pp. 16 to 17)    Patent Document 2: International Publication WO 2004/36655 (pp. 5 to 6)    Patent Document 3: JP-T-9-511103 (pp. 13 to 15)